FP-10 to lube big bore slugs?

Hey there fellow airgunners/ big bore enthusiasts. My question today is do you pay the extra amount to have the caster lube your slugs? Does it even really make a difference? I used to use fp-10 on my ammo I shot through my gaska tj barrels. Would this be sufficient to lube my big bore slugs as well? Any information, practical experience or advice is much appreciated. TIA.